Diagnosis of Bovine Respiratory Disease in feedlot cattle using blood 1H NMR metabolomics.

Current diagnosis methods for Bovine Respiratory Disease (BRD) in feedlots have a low diagnostic accuracy. The current study aimed to search for blood biomarkers of BRD using 1H NMR metabolomics and determine their accuracy in diagnosing BRD. Animals with visual signs of BRD (n = 149) and visually healthy (non-BRD; n = 148) were sampled for blood metabolomics analysis. Lung lesions indicative of BRD were scored at slaughter. Non-targeted 1H NMR metabolomics was used to develop predictive algorithms for disease classification using classification and regression trees. In the absence of a gold standard for BRD diagnosis, six reference diagnosis methods were used to define an animal as BRD or non-BRD. Sensitivity (Se) and specificity (Sp) were used to estimate diagnostic accuracy (Acc). Blood metabolomics demonstrated a high accuracy at diagnosing BRD when using visual signs of BRD (Acc = 0.85), however was less accurate at diagnosing BRD using rectal temperature (Acc = 0.65), lung auscultation score (Acc = 0.61) and lung lesions at slaughter as reference diagnosis methods (Acc = 0.71). Phenylalanine, lactate, hydroxybutyrate, tyrosine, citrate and leucine were identified as metabolites of importance in classifying animals as BRD or non-BRD. The blood metabolome classified BRD and non-BRD animals with high accuracy and shows potential for use as a BRD diagnosis tool.

Alpharma Beef Cattle Nutrition Symposium: predictability of feedlot cattle growth performance.

Predicting performance is vital to management and marketing decisions in commercial feedlots. Agreement between performance predicted from NE equations or empirical regression relationships and actual performance is generally very good, suggesting that factors affecting performance by finishing cattle are fairly well documented. The challenge for feedlot managers is to predict performance with limited information at the start of the feeding period. Data on sex and initial shrunk BW (ISBW) are typically available when cattle start on feed. Relationships between ISBW, sex, and performance were evaluated using 3,363 pen records collected over 4 yr from 3 commercial feedlots in the Texas Panhandle. Mixed-model regression was used to account for random effects of feedlot × season × year and fixed effects of ISBW (range = 227 to 451 kg), sex (steer or heifer), and ISBW × sex (P < 0.10 for all variables evaluated). Previously developed equations indicated that with intercept and slope adjustments for sex, ISBW accounted for 76 and 84% of the variation in DMI and final shrunk BW (FSBW), respectively. Similarly, newly developed regression equations that included ISBW, sex, and ISBW × sex accounted for 46 and 81% of the variation in ADG and HCW, respectively. Initial BW was negatively related to G:F (R(2) = 0.22). Including early DMI data (DMI from d 8 to 28) increased R(2) and decreased prediction error for DMI, indicating that updating predictions with interim intake data might prove beneficial. An independent data set (781 lots of steers and heifers) collected during 1 yr from 2 Texas Panhandle feedlots was used to validate equations developed with the larger database. Dry matter intake predicted from ISBW and sex accounted for 69% of the variation in observed DMI (SE of prediction = 0.47; mean bias = 0.42 kg). Predicting DMI with ISBW, sex, and DMI from d 8 to 28 of the feeding period increased r(2) to 0.76 and slightly decreased the SE of prediction (0.42 kg), but the equation had a strong linear bias (-0.174; P < 0.001). The r(2) values for regression of observed on predicted ADG, G:F, FSBW, and HCW were 0.37, 0.08, 0.74, and 0.73, respectively, with positive mean bias (underprediction for all equations). Average daily gain calculated with NE equations from predicted DMI (ISBW and sex equation) and predicted FSBW had a similar r(2) (0.38) but less mean bias (-0.08 kg) than ADG predicted directly from ISBW and sex. Adjustments to equations for animal type, health, and management effects would likely improve predictions. Nonetheless, results suggest that predicting performance from initial BW with adjustments for steers vs. heifers should have considerable utility in practical settings.

Development and evaluation of feeding-period average dry matter intake prediction equations from a commercial feedlot database.

Intake prediction equations were developed from a commercial feedlot database consisting of 3,363 pen means collected from 3 feedlots over a 4-yr period. The objective was to predict feeding-period average DMI from variables known at the start of the feeding period, including initial BW, sex, and average DMI from d 8 to 28 of the feeding period. Equations were evaluated within the same database using bootstrapping and cross-validation techniques. Bootstrapping evaluations of equations that included initial BW and sex explained approximately 57.0 to 73.2% of the variation in observed DMI with 90.5 to 96.6% accuracy, but DMI was overpredicted by 0.21 kg/d. Accuracy and precision improved with addition to the models of average DMI from d 8 to 28 of the feeding period; these models accounted for 68.0 to 83.0% of variation in observed DMI with model accuracy between 95.2 and 99.5% and overprediction of DMI by 0.05 kg/d. Cross-validation of developed equations confirmed the robust nature of chosen variables and the decrease in prediction error as sex and average DMI from d 8 to 28 were added to models based on initial shrunk BW (SBW). Bootstrapping and cross-validation evaluations were also conducted on the NRC (1996) NE(m)-based intake prediction equations with and without the NRC-recommended 4% decrease in predicted DMI and a 12% increase in dietary NE(m) concentration associated with the feeding of monensin. The average metabolic SBW used in these equations was computed from initial SBW and a predicted final SBW developed from the pen database. When these evaluations were performed, model precision decreased compared with simpler equations that included initial BW and sex, but using both adjustments for use of monensin improved the accuracy of the NRC equation. Nonetheless, the systematic bias proportion of the mean square error of prediction for bootstrapping analyses increased from 4.6 to 11.1% in the model with no adjustments to 16.3 to 38.9% in the model with both monensin adjustments, demonstrating these adjustments are less than optimal. Overall, variables that are typically available to feedlot managers when cattle are started on feed (e.g., initial BW, sex, and an early indication of DMI) were important predictors of feeding-period average DMI by pens of cattle.

Effects of varying bulk densities of steam-flaked corn and dietary roughage concentration on in vitro fermentation, performance, carcass quality, and acid-base balance measurements in finishing steers.

Effects of varying bulk densities of steam-flaked corn (SFC) and level of inclusion of roughage in feedlot diets were evaluated in 3 experiments. In Exp. 1, a total of 128 beef steers were used in a 2 x 2 factorial arrangement to evaluate the effects of bulk density of SFC (335 or 386 g/L) and roughage concentration (6 or 10% ground alfalfa hay, DM basis) on performance and carcass characteristics. No interactions were observed between bulk density and roughage concentration for performance data. From d 0 to the end, cattle fed the 335 g/L SFC had greater overall G:F (P = 0.04) than those fed the 386 g/L SFC, with tendencies (P < 0.10) for improved G:F with the lighter flake weight evident at all 35-d intervals throughout the feeding period. Dry matter intake was less for cattle fed 6 vs. 10% roughage from d 0 to 35 (P = 0.03) and d 0 to 70 (P = 0.05), but not for the overall feeding period. Feeding 6 vs. 10% ground alfalfa as the roughage source tended (P = 0.09) to improve overall G:F. Treatment effects on carcass measurements were generally not significant (P > 0.20). In Exp. 2, the effects of bulk density of SFC (283, 335, or 386 g/L) and 6 or 10% ground alfalfa hay on IVDMD and in vitro pH were evaluated at 6, 12, 18, and 24 h of incubation. With a reduced-strength buffer in vitro fermentation system, pH increased (P < 0.01) with increasing bulk density at 6 and 12 h, and IVDMD decreased (P < 0.03) as bulk density increased. In contrast, in a normal-strength buffer system, there were no treatment differences (P > 0.23) for IVDMD. In Exp. 3, two diets that varied in bulk density of SFC and roughage concentration (335 g/L SFC with 6% alfalfa hay vs. 386 g/L SFC with 10% alfalfa hay) were compared for their effects on the pattern of feed intake and the acid-base balance in Holstein steers (12/treatment). No differences (P > 0.10) between treatments were noted for blood gases or urine pH; however, day effects (P < 0.02) were detected for blood pH, partial pressure of CO(2), and urine pH, which generally decreased (P < 0.05) with an increasing time on feed. The 2 treatments had little effect on the pattern of feed intake within the sampling days, with the exception that the 386 g/L SFC with 10% alfalfa hay diet increased (P < 0.05) the percentage of total DMI consumed at 1 and 6 h after feeding on d 14. Within the ranges of bulk density and roughage level studied, 335 g/L SFC with 6% alfalfa hay yielded the optimal animal performance, with limited effects on in vitro fermentation and the acid-base balance.

Evaluation of the National Research Council (1996) dry matter intake prediction equations and relationships between intake and performance by feedlot cattle.

Intake prediction equations of NRC based on initial BW and dietary NE(m) concentration were evaluated with a commercial feedlot database consisting of 3,363 pen means collected from 3 feedlots over a 4-yr period. The DMI predicted by NRC equations had significant (P < 0.01) mean and linear biases across the range of observed DMI in the database. In general, DMI was overpredicted by the NRC equations. Adjustment of the NE(m)-based prediction by use of a 12% increase in NE(m) concentration and a 4% decrease in predicted DMI associated with the feeding of monensin decreased bias. Dry matter intake predicted by the NE(m)-based monensin-adjusted, NE(m)- based, and initial BW equations explained 67, 66, and 64% of the variation in observed DMI, respectively. Relationships between ADG and G:F with DMI as a percentage of BW and NE(g) intake also were examined in the same data set. Across the wide range of average shrunk BW in the database (334.4 to 548.0 kg), ADG was positively related to DMI as a percentage of BW (P < 0.01); however, this relationship was not strong (r(2) = 0.17). Likewise, G:F showed little relationship with DMI as a percentage of BW (P < 0.01; r(2) = 0.05). By accounting for differences in maintenance energy requirements of pens with varying average BW, NE(g) intake was strongly and positively related to ADG (linear and quadratic, P < 0.01; R(2) = 0.70); however, G:F showed little relationship with NE(g) intake (P = 0.02; r(2) = 0.01). Our evaluations with measurements of DMI by cattle in commercial feedlots indicated the shortcomings of current published equations for predicting DMI and suggest the need for development of new equations with improved accuracy and precision. Furthermore, our data indicate that increasing NE(g) in- take increased ADG in a quadratic manner but did not affect G:F by pens of cattle in feedlots. These findings suggest a diminishing returns effect of energy intake on energy retention.

Effects of duration of zilpaterol hydrochloride feeding and days on the finishing diet on feedlot cattle performance and carcass traits.

British and British x Continental steers (n = 560; initial BW = 339.4 +/- 1.76 kg) were used in a serial slaughter study with a completely random design to evaluate effects of zilpaterol hydrochloride (ZH; 8.33 mg/kg of dietary DM basis) on performance and carcass characteristics. Treatments were arranged in a 4 x 4 factorial (112 pens; 7 pens/treatment; 5 steers/pen) and included duration of ZH feeding (0, 20, 30, or 40 d before slaughter plus a 3-d ZH withdrawal period) and days on feed (DOF) before slaughter (136, 157, 177, and 198 d). No duration of ZH feeding x slaughter group interactions were detected for the performance measurements (P > 0.10). Final BW did not differ (P = 0.15) between the 0-d group and the average of the 3 ZH groups, but ADG was greater for the average of the 3 ZH groups during the period in which ZH diets were fed (P < 0.01) and for the overall feeding period (P = 0.05). As duration of ZH feeding increased, DMI decreased (P = 0.01) and G:F increased linearly (P < 0.01). With the exception of KPH (P = 0.022), no duration of ZH feeding x slaughter group interactions (P > 0.10) were detected for carcass characteristics. Regardless of the duration of ZH feeding, cattle fed ZH had greater HCW (P < 0.01), greater dressing percent (P < 0.01), less 12th-rib fat (P < 0.01), larger LM area (P < 0.01), less KPH (P = 0.03), and lower yield grade (P < 0.01) than the 0-d cattle. The 0-d group had greater marbling scores (P < 0.01) than cattle fed ZH diets, with a tendency for a linear decrease in marbling score (P = 0.10) as duration of ZH feeding was extended. A greater percentage of carcasses in the 0-d group graded USDA Choice or greater (P < 0.01) than in the 3 ZH groups, whereas the percentage of Select carcasses was greater (P = 0.01) for the 3 ZH groups. From d 0 to end (P = 0.04) and during the last 43 d on feed (P < 0.01), ADG responded quadratically to DOF before slaughter. No differences were detected among slaughter groups for DMI for the entire trial period; however, a quadratic response (P = 0.02) was observed for the final 43 d before slaughter. A quadratic response was also detected for the final 43 d before slaughter (P < 0.01) and from d 0 to end (P = 0.02) for G:F. Final BW, HCW, dressing percent, and 12th-rib fat increased linearly (P < 0.01) as DOF before slaughter increased. Our results indicate that no substantial effects on performance and carcass measurements were observed when ZH was fed for 30 or 40 d as opposed to 20 d, and that effects of ZH generally did not interact with DOF before slaughter.

Effects of 2-hydroxy-4-(methylthio)-butanoic acid on performance and carcass characteristics of finishing beef cattle and on fermentation in continuous culture.

Three experiments were conducted to evaluate the effects of feeding 2-hydroxy-4- (methylthio)-butanoic acid (HMTBA) on performance and carcass characteristics of feedlot cattle and on microbial fermentation in a continuous-culture system. In Exp. 1, 160 crossbred steers (initial BW = 385 +/- 10.3 kg) were assigned to 4 treatments consisting of control (0% HMTBA) or 3 diets containing HMTBA (0.069, 0.137, and 0.204%; DM basis) in a randomized complete block design. As the percent of HMTBA increased in the diet, final BW (P = 0.069), final BW adjusted to a constant dressing percent (P = 0.063), and overall ADG (P = 0.099) tended to decrease linearly. Overall DMI decreased linearly (P < or = 0.006) with increasing HMTBA dose. No differences (P > or = 0.10) were noted for carcass characteristics, except for a tendency (P = 0.078) for a linear increase in the percentage of cattle grading USDA Choice with increasing HMTBA dose. In Exp. 2, 80 crossbred steers (initial BW = 450 +/- 17 kg) in a randomized complete block design were assigned to a control (0% HMTBA) diet or to a diet in which the concentrations of HMTBA were gradually increased from 0.036 to 0.212% of DM over a 50-d period. The HMTBA-containing diet tended to decrease DMI (P = 0.132), but G:F (P = 0.319) for the overall feeding period, carcass measurements, and USDA quality grade (P > or = 0.149) did not differ between treatments. In Exp. 3, continuous culture fermenters (n = 5/treatment) were used to determine the effects of HMTBA (control vs. 0.24% HMTBA) on microbial fermentation. No differences (P > or = 0.31) were detected between treatments in ruminal OM digestibility, microbial N synthesis, pH, ammonia, molar proportions of VFA, or effluent concentration of selected long-chain fatty acids. These results suggest that HMTBA decreased DMI by feedlot steers fed a steam-flaked corn-based diet in a dose-dependent manner; however, gradually increasing the dose over time seemed to moderate effects on DMI. No major changes in microbial fermentation in continuous culture were observed with HMTBA at 0.24% of dietary DM, suggesting effects of HMTBA on DMI were not likely associated with changes in ruminal digestion or fermentation.

Effects of ractopamine hydrochloride on performance, rate and variation in feed intake, and acid-base balance in feedlot cattle.

Two experiments evaluated effects of ractopamine hydrochloride (RAC) on performance, intake patterns, and acid-base balance of feedlot cattle. In Exp. 1, 360 crossbred steers (Brangus, British, and British x Continental breeding; initial BW = 545 kg) were used in a study with a 3 x 3 factorial design to study the effects of dose [0, 100, or 200 mg/(steer x d) of RAC] and duration (28, 35, or 42 d) of feeding of RAC in a randomized complete block design (9 treatments, 8 pens/treatment). No dose x duration interactions were detected (P > 0.10). As RAC dose increased, final BW (FBW; P = 0.01), ADG (P < 0.01), and G:F (P < 0.01) increased linearly. As duration of feeding increased, ADG increased quadratically (P = 0.04), with tendencies for quadratic effects for FBW (P = 0.06), DMI (P = 0.07), and G:F (P = 0.09). Hot carcass weight increased linearly (P = 0.02) as dose of RAC increased. Thus, increasing the dose of RAC from 0 to 200 mg/(steer x d) and the duration of feeding from 28 to 42 d improved feedlot performance, although quadratic responses for duration of feeding indicated little improvement as the duration was extended from 35 to 42 d. In Exp. 2, 12 crossbred beef steers (BW = 593 kg) were used in a completely random design to evaluate the effects of RAC [0 or 200 mg/(steer x d) for 30 d; 6 steers/treatment] on rate of intake, daily variation in intake patterns, and acid-base balance. To assess intake patterns, absolute values of daily deviations in feed delivered to each steer relative to the total quantity of feed delivered were analyzed as repeated measures. There were no differences (P > 0.10) in feedlot performance, urine pH, blood gas measurements, or variation in intake patterns between RAC and control cattle, but steers fed RAC had increased (P = 0.04) LM area, decreased (P = 0.03) yield grade, and increased (P < 0.10) time to consume 50 and 75% of daily intake relative to control steers. Our results suggest that feeding RAC for 35 d at 200 mg/(steer x d) provided optimal performance, and no effects on acid-base balance or variation in intake patterns of finishing steers were noted with RAC fed at 200 mg/(steer x d) over a 30-d period.

Effects of Saccharomyces cerevisiae subspecies boulardii CNCM I-1079 on feed intake by healthy beef cattle treated with florfenicol and on health and performance of newly received beef heifers.

The effects of a live yeast supplement [Saccharomyces cerevisiae subspecies boulardii CNCM I-1079; ProTernative Stress Formula (PTSF) yeast, Ivy Natural Solutions, Overland Park, KS] on DMI, performance, and health of beef cattle were evaluated in 3 experiments. In Exp. 1, a pilot study was conducted with 10 healthy beef steers fed a 65% concentrate diet to evaluate the effects of florfenicol (s.c. in the neck vs. sterile water injection) on DMI. Steers injected with florfenicol had 15.6 (P = 0.092) and 22.2% (P = 0.015) decreases in DMI compared with controls on the day of and day after injection, respectively, with no differences for the remainder of the 7-d period. In the main study of Exp. 1, healthy beef steers (6 pens of 5 steers each/treatment) were fed the control or PTSF yeast diets (0.5 g of yeast x steer(-1) x d(-1)) for 5 d before being injected s.c. with florfenicol. Compared with the 5 d before injection, DMI decreased after injection, but it did not differ (P > 0.66) between treatments on the day of and day after injection. By the second day after injection, DMI tended (P = 0.107) to increase for steers fed PTSF yeast vs. control steers, with a trend for a similar pattern on the third day after injection (P = 0.197). No differences were noted between treatments for the remainder of the 7-d period or for the subsequent 2 wk. In Exp. 2, 3 loads of beef heifers (277 heifers; average initial BW = 230.3 kg) were shipped from auction barns and assigned randomly to 1 of 2 treatments (5 pens/treatment in each load) during 35-d receiving periods: 1) control = 65% concentrate receiving diet; or 2) PTSF yeast = 65% concentrate receiving diet with PTSF yeast added to supply 0.5 g of yeast x heifer(-1) x d(-1). All heifers were treated with florfenicol on arrival, and PTSF yeast heifers received approximately 1 g of yeast via an oral paste at the time of processing. Averaged over the 3 loads, treatments did not affect (P > or = 0.12) DMI, ADG, or G:F during the 35-d period, but the percentage of cattle treated once or more for bovine respiratory disease (BRD) was greater for control (P = 0.04) than for PTSF yeast heifers (24.0 vs. 13.78% respectively). In Exp. 3, 2 loads of beef heifers (180 heifers; average initial BW = 209.0 kg) that were not treated with antibiotic at the time of arrival processing were fed a 70% concentrate receiving diet and assigned the same 2 treatments as in Exp. 2. No differences (P > 0.72) were noted between treatments in ADG, DMI, and G:F for the 35-d receiving period, and BRD morbidity pooled across loads did not differ between treatments (40.2 vs. 33.1% for control vs. PTSF yeast). Providing PTSF yeast in an oral paste at the time of processing combined with the addition of 0.5 g of yeast x animal(-1) x d(-1) in the diet had little effect on receiving period performance; however, it decreased BRD morbidity in heifers given florfenicol on arrival but was without effect on BRD morbidity in heifers that did not receive a prophylactic antibiotic.

Effects of an artificial sweetener on health, performance, and dietary preference of feedlot cattle.

Two experiments examined the effects of a saccharin-based artificial sweetener (Sucram) on health, performance, and dietary preference of feedlot cattle. In Exp. 1, 200 steer calves (initial BW = 190.4 +/- 1.47 kg) were fed a 65% concentrate diet supplemented with or without 200 mg of Sucram/kg (DM basis) during a 56-d receiving-growing period. Feeding Sucram did not affect overall (P = 0.19) DMI; however, from d 29 to 56, there was a trend (P = 0.10) for increased DMI with Sucram (5.71 vs. 6.02 kg/d, respectively). From d 0 to 28 and d 0 to 56, there were trends (P = 0.11 and 0.12, respectively) for increased ADG and for increased d-56 BW (P = 0.07) for calves fed Sucram. No differences were detected (P = 0.82) for receiving (REC) period morbidity. During the finishing (FIN) period, 180 steers from the REC period were assigned (9 pens/treatment in a 2 x 2 factorial design) to the following treatments: 1) control REC/control FIN; 2) control REC/Sucram FIN; 3) Sucram REC/control FIN; and 4) Sucram REC/ Sucram FIN. Over the FIN period, ADG tended (P = 0.12) to be greater for Sucram; however, carcass-adjusted ADG did not differ among treatments. Daily DMI was affected by a REC x FIN interaction (P = 0.08), which was the result of greater DMI by cattle in the Sucram REC/Sucram FIN treatment and decreased DMI by cattle in the Sucram REC/control FIN treatment. In general, changes in carcass characteristics were minor. In Exp. 2, 12 steers (initial BW = 395.6 +/- 6.17 kg) were used in a simultaneously replicated 3 x 3 Latin square preference test. Each square consisted of 3 pens, with 2 steers/pen, and 3 time periods. Bunks had dividers at their midpoint, and equal quantities of diet (as-fed basis) were delivered randomly on either side of the divider daily. Treatments were: 1) control; 2) Sucram = basal diet supplemented with 200 mg of Sucram/kg of DM; and 3) choice = control and Sucram on separate sides of the divider. Dietary preference differed on d 1 (P = 0.01) and d 3 (P = 0.02) for control vs. choice and Sucram vs. choice, with the choice group consuming 0.49 and 1.72 kg of DM more of the Sucram diet than the control diet, respectively. This effect, however, was not consistent across days, and average DMI did not differ (P = 0.81) among treatments. Addition of Sucram to the diet of newly received cattle tended to increase receiving period ADG; however, its effects on morbidity, finishing performance, and dietary preference were limited.

The efficacy of a vitamin D(3) metabolite for improving the myofibrillar tenderness of meat from Bos indicus cattle.

The influence of a once only administration of a metabolite of vitamin D(3) (HY·D(®)-25-hydroxy vitamin D(3)) on myofibrillar meat tenderness in Australian Brahman cattle was studied. Ninety-six Brahman steers of three phenotypes (Indo-Brazil, US and US/European) and with two previous hormonal growth promotant (HGP) histories (implanted or not implanted with Compudose(®)) were fed a standard feedlot ration for 70d. Treatment groups of 24 steers were offered daily 10g/head HY·D(®) (125mg 25-hydroxyvitamin D(3)) for 6, 4, or 2d before slaughter. One other group of 24 steers was given the basal diet without HY·D(®). Feed lot performance, blood and muscle samples and carcass quality data were collected at slaughter. Calcium, magnesium, potassium, sodium, iron and Vitamin D(3) metabolites were measured in plasma and longissimus dorsi muscle. Warner-Bratzler (WB) shear force (peak force, initial yield) and other objective meat quality measurements were made on the longissimus dorsi muscle of each steer after ageing for 1, 7 and 14d post-mortem at 0-2°C. There were no significant effects of HY·D(®) supplements on average daily gain (ADG, 1.28-1.45kg/d) over the experimental period. HY·D(®) supplements given 6d prior to slaughter resulted in significantly higher (P<0.05) initial yield values compared to supplements given 2d prior to slaughter. Supplementation had no significant effect on meat colour, ultimate pH, sarcomere length, cooking loss, instron compression or peak force. There was a significant treatment (HY·D(®)) by phenotype/HGP interaction for peak force (P=0.028), in which Indo-Brazil steers without previous HGP treatment responded positively (increased tenderness) to HY·D(®) supplements at 2d when compared with Indo-Brazil steers previously given HGP. There were no significant effects of treatment on other phenotypes. HY·D(®) supplements did not affect muscle or plasma concentrations of calcium, potassium or sodium, but did significantly decrease plasma magnesium and iron concentrations when given 2d before slaughter. There were no detectable amounts of 25-hydroxyvitamin D(3) in the blood or muscle of any cattle at slaughter.